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KB-5794: Nessus 5.2.9 scan vulnerability, flagging 'server signing' port 445 required for Samba

Centrify DirectControl ,   Centrify DirectControl Plugins ,  

15 October,15 at 12:11 AM

Applies to:

Centrify DirectControl with Centrify Samba 4.5.9 on All Linux Servers


While running a third party scanning tool called Nessus 5.2.9 for audit purposes on a host with Centrify DirectControl and Centrify Samba, it flag an alert that signing is set to not required on the remote SMB server (see attached output).


If host settings in smb.conf is set to ‘server signing = disabled’, signing is not required on the remote SMB server which can allow man-in-the-middle attacks against the SMB server.

See Resolution.

  • Edit smb.conf and modify/add the parameter ‘server signing = mandatory’ and ‘smb encrypt = auto’.
The above settings will configure samba to always require its clients to generate a signature on the SMB packets, and the samba server will then do the same.
  • Restart samba service.
# /etc/init.d/centrifydc-samba restart
  • Re-run
# /usr/share/centrifydc/bin/
  • Re-run Nessus scan.

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